package concurrency;//: concurrency/SynchronizationComparisons.java
// Comparing the performance of explicit Locks
// and Atomics versus the synchronized keyword.

import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;
import java.util.*;

import static net.mindview.util.Print.*;

abstract class Accumulator {
    public static long cycles = 50000L;
    // Number of Modifiers and Readers during each test:
    private static final int N = 4;
    public static ExecutorService exec =
            Executors.newFixedThreadPool(N * 2);
    private static CyclicBarrier barrier =
            new CyclicBarrier(N * 2 + 1);
    protected volatile int index = 0;
    protected volatile long value = 0;
    protected long duration = 0;
    protected String id = "error";
    protected final static int SIZE = 100000;
    protected static int[] preLoaded = new int[SIZE];

    static {
        // Load the array of random numbers:
        Random rand = new Random(47);
        for (int i = 0; i < SIZE; i++)
            preLoaded[i] = rand.nextInt();
    }

    public abstract void accumulate();

    public abstract long read();

    private class Modifier implements Runnable {
        public void run() {
            for (long i = 0; i < cycles; i++)
                accumulate();
            try {
                barrier.await();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }

    private class Reader implements Runnable {
        private volatile long value;

        public void run() {
            for (long i = 0; i < cycles; i++)
                value = read();
            try {
                barrier.await();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }

    public void timedTest() {
        long start = System.nanoTime();
        for (int i = 0; i < N; i++) {
            exec.execute(new Modifier());
            exec.execute(new Reader());
        }
        try {
            barrier.await();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        duration = System.nanoTime() - start;
        printf("%-13s: %13d\n", id, duration);
    }

    public static void
    report(Accumulator acc1, Accumulator acc2) {
        printf("%-22s: %.2f\n", acc1.id + "/" + acc2.id,
                (double) acc1.duration / (double) acc2.duration);
    }
}

class BaseLine extends Accumulator {
    {
        id = "BaseLine";
    }

    public void accumulate() {
        value += preLoaded[index++];
        if (index >= SIZE) index = 0;
    }

    public long read() {
        return value;
    }
}

class SynchronizedTest extends Accumulator {
    {
        id = "synchronized";
    }

    public synchronized void accumulate() {
        value += preLoaded[index++];
        if (index >= SIZE) index = 0;
    }

    public synchronized long read() {
        return value;
    }
}

class LockTest extends Accumulator {
    {
        id = "Lock";
    }

    private Lock lock = new ReentrantLock();

    public void accumulate() {
        lock.lock();
        try {
            value += preLoaded[index++];
            if (index >= SIZE) index = 0;
        } finally {
            lock.unlock();
        }
    }

    public long read() {
        lock.lock();
        try {
            return value;
        } finally {
            lock.unlock();
        }
    }
}

class AtomicTest extends Accumulator {
    {
        id = "Atomic";
    }

    private AtomicInteger index = new AtomicInteger(0);
    private AtomicLong value = new AtomicLong(0);

    public void accumulate() {
        // Oops! Relying on more than one Atomic at
        // a time doesn't work. But it still gives us
        // a performance indicator:
        int i = index.getAndIncrement();
        value.getAndAdd(preLoaded[i]);
        if (++i >= SIZE)
            index.set(0);
    }

    public long read() {
        return value.get();
    }
}

public class SynchronizationComparisons {
    static BaseLine baseLine = new BaseLine();
    static SynchronizedTest synch = new SynchronizedTest();
    static LockTest lock = new LockTest();
    static AtomicTest atomic = new AtomicTest();

    static void test() {
        print("============================");
        printf("%-12s : %13d\n", "Cycles", Accumulator.cycles);
        baseLine.timedTest();
        synch.timedTest();
        lock.timedTest();
        atomic.timedTest();
        Accumulator.report(synch, baseLine);
        Accumulator.report(lock, baseLine);
        Accumulator.report(atomic, baseLine);
        Accumulator.report(synch, lock);
        Accumulator.report(synch, atomic);
        Accumulator.report(lock, atomic);
    }

    public static void main(String[] args) {
        int iterations = 5; // Default
        if (args.length > 0) // Optionally change iterations
            iterations = new Integer(args[0]);
        // The first time fills the thread pool:
        print("Warmup");
        baseLine.timedTest();
        // Now the initial test doesn't include the cost
        // of starting the threads for the first time.
        // Produce multiple data points:
        for (int i = 0; i < iterations; i++) {
            test();
            Accumulator.cycles *= 2;
        }
        Accumulator.exec.shutdown();
    }
} /* Output: (Sample)
Warmup
BaseLine     :      34237033
============================
Cycles       :         50000
BaseLine     :      20966632
synchronized :      24326555
Lock         :      53669950
Atomic       :      30552487
synchronized/BaseLine : 1.16
Lock/BaseLine         : 2.56
Atomic/BaseLine       : 1.46
synchronized/Lock     : 0.45
synchronized/Atomic   : 0.79
Lock/Atomic           : 1.76
============================
Cycles       :        100000
BaseLine     :      41512818
synchronized :      43843003
Lock         :      87430386
Atomic       :      51892350
synchronized/BaseLine : 1.06
Lock/BaseLine         : 2.11
Atomic/BaseLine       : 1.25
synchronized/Lock     : 0.50
synchronized/Atomic   : 0.84
Lock/Atomic           : 1.68
============================
Cycles       :        200000
BaseLine     :      80176670
synchronized :    5455046661
Lock         :     177686829
Atomic       :     101789194
synchronized/BaseLine : 68.04
Lock/BaseLine         : 2.22
Atomic/BaseLine       : 1.27
synchronized/Lock     : 30.70
synchronized/Atomic   : 53.59
Lock/Atomic           : 1.75
============================
Cycles       :        400000
BaseLine     :     160383513
synchronized :     780052493
Lock         :     362187652
Atomic       :     202030984
synchronized/BaseLine : 4.86
Lock/BaseLine         : 2.26
Atomic/BaseLine       : 1.26
synchronized/Lock     : 2.15
synchronized/Atomic   : 3.86
Lock/Atomic           : 1.79
============================
Cycles       :        800000
BaseLine     :     322064955
synchronized :     336155014
Lock         :     704615531
Atomic       :     393231542
synchronized/BaseLine : 1.04
Lock/BaseLine         : 2.19
Atomic/BaseLine       : 1.22
synchronized/Lock     : 0.47
synchronized/Atomic   : 0.85
Lock/Atomic           : 1.79
============================
Cycles       :       1600000
BaseLine     :     650004120
synchronized :   52235762925
Lock         :    1419602771
Atomic       :     796950171
synchronized/BaseLine : 80.36
Lock/BaseLine         : 2.18
Atomic/BaseLine       : 1.23
synchronized/Lock     : 36.80
synchronized/Atomic   : 65.54
Lock/Atomic           : 1.78
============================
Cycles       :       3200000
BaseLine     :    1285664519
synchronized :   96336767661
Lock         :    2846988654
Atomic       :    1590545726
synchronized/BaseLine : 74.93
Lock/BaseLine         : 2.21
Atomic/BaseLine       : 1.24
synchronized/Lock     : 33.84
synchronized/Atomic   : 60.57
Lock/Atomic           : 1.79
*///:~
